A) Field of the Invention
The present invention relates to a semiconductor light-emitting device and a method for manufacturing the same.
B) Description of the Related Art
A nitride semiconductor light-emitting diode (LED) using GaN or GaN-containing material can emit ultraviolet or blue light and is able to emit white light by using phosphor. An LED capable of outputting high power white light can be used also for illumination.
Though sapphire is generally used as a growth substrate for nitride semiconductor, sapphire is poor in heat dissipation due to its low thermal conductivity. As a structure for improving heat dissipation, the flip-chip structure where a semiconductor layer is bonded on a heat dissipative support substrate, with the sapphire substrate being disposed opposite side, is known.
In emitting light from the flip-chip structure, there occurs light reflection at the rear surface of the sapphire substrate, which lowers the efficiency of light emission. It has been proposed to remove the sapphire substrate by laser lift-off or abrasion after semiconductor lamination grown on the sapphire substrate is bonded on a support substrate. Also, there is proposed to form electrode structure having a shape serving both as wiring for current spreading and as n-side electrode for the diode, on the element upper surface (see, for example, WO 2005/071763, family US 2007/0278508, JP P2007-519246).
It is not easy to obtain uniform current distribution in a nitride semiconductor light-emitting device having a large chip area. Non-uniform current distribution increases the forward voltage drop and lowers the quantum efficiency. It is known to form, for example, a semi-transparent metallization layer over the entire surface of a chip for improving current spreading. However, it is necessary to have some thickness, for example 100 nm or more, for the semi-transparent metallization to achieve current spreading effect. Then, the semi-transparent metallization will absorb part of output light, to decrease the output power.